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[audio utils] fix fft_bin_width computation (#36603)

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* fix fft_bin_width computation

* update docstring + enforce correct params

* update test with correct value

* udpate test

* update feature extractors for concerned models

* update

* make

* udpate docstring

* udpate docstring
This commit is contained in:
eustlb
2025-03-27 15:20:02 +01:00
committed by GitHub
parent e97c760006
commit fb8e6c50e4
5 changed files with 45 additions and 31 deletions
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10
src/transformers/audio_utils.py
View File

@@ -293,7 +293,7 @@ def mel_filter_bank(
Args:
num_frequency_bins (`int`):
Number of frequencies used to compute the spectrogram (should be the same as in `stft`).
Number of frequency bins (should be the same as `n_fft // 2 + 1` where `n_fft` is the size of the Fourier Transform used to compute the spectrogram).
num_mel_filters (`int`):
Number of mel filters to generate.
min_frequency (`float`):
@@ -317,6 +317,12 @@ def mel_filter_bank(
if norm is not None and norm != "slaney":
raise ValueError('norm must be one of None or "slaney"')
if num_frequency_bins < 2:
raise ValueError(f"Require num_frequency_bins: {num_frequency_bins} >= 2")
if min_frequency > max_frequency:
raise ValueError(f"Require min_frequency: {min_frequency} <= max_frequency: {max_frequency}")
# center points of the triangular mel filters
mel_min = hertz_to_mel(min_frequency, mel_scale=mel_scale)
mel_max = hertz_to_mel(max_frequency, mel_scale=mel_scale)
@@ -325,7 +331,7 @@ def mel_filter_bank(
if triangularize_in_mel_space:
# frequencies of FFT bins in Hz, but filters triangularized in mel space
fft_bin_width = sampling_rate / (num_frequency_bins * 2)
fft_bin_width = sampling_rate / ((num_frequency_bins - 1) * 2)
fft_freqs = hertz_to_mel(fft_bin_width * np.arange(num_frequency_bins), mel_scale=mel_scale)
filter_freqs = mel_freqs
else:

4
src/transformers/models/audio_spectrogram_transformer/feature_extraction_audio_spectrogram_transformer.py
View File

@@ -91,7 +91,7 @@ class ASTFeatureExtractor(SequenceFeatureExtractor):
if not is_speech_available():
mel_filters = mel_filter_bank(
num_frequency_bins=256,
num_frequency_bins=257,
num_mel_filters=self.num_mel_bins,
min_frequency=20,
max_frequency=sampling_rate // 2,
@@ -101,7 +101,7 @@ class ASTFeatureExtractor(SequenceFeatureExtractor):
triangularize_in_mel_space=True,
)
self.mel_filters = np.pad(mel_filters, ((0, 1), (0, 0)))
self.mel_filters = mel_filters
self.window = window_function(400, "hann", periodic=False)
def _extract_fbank_features(

4
src/transformers/models/seamless_m4t/feature_extraction_seamless_m4t.py
View File

@@ -74,7 +74,7 @@ class SeamlessM4TFeatureExtractor(SequenceFeatureExtractor):
self.stride = stride
mel_filters = mel_filter_bank(
num_frequency_bins=256,
num_frequency_bins=257,
num_mel_filters=self.num_mel_bins,
min_frequency=20,
max_frequency=sampling_rate // 2,
@@ -84,7 +84,7 @@ class SeamlessM4TFeatureExtractor(SequenceFeatureExtractor):
triangularize_in_mel_space=True,
)
self.mel_filters = np.pad(mel_filters, ((0, 1), (0, 0)))
self.mel_filters = mel_filters
self.window = window_function(400, "povey", periodic=False)
super().__init__(feature_size=feature_size, sampling_rate=sampling_rate, padding_value=padding_value, **kwargs)

4
src/transformers/models/speech_to_text/feature_extraction_speech_to_text.py
View File

@@ -91,7 +91,7 @@ class Speech2TextFeatureExtractor(SequenceFeatureExtractor):
if not is_speech_available():
mel_filters = mel_filter_bank(
num_frequency_bins=256,
num_frequency_bins=257,
num_mel_filters=self.num_mel_bins,
min_frequency=20,
max_frequency=sampling_rate // 2,
@@ -101,7 +101,7 @@ class Speech2TextFeatureExtractor(SequenceFeatureExtractor):
triangularize_in_mel_space=True,
)
self.mel_filters = np.pad(mel_filters, ((0, 1), (0, 0)))
self.mel_filters = mel_filters
self.window = window_function(400, "povey", periodic=False)
def _extract_fbank_features(

54
tests/utils/test_audio_utils.py
View File

@@ -194,26 +194,38 @@ class AudioUtilsFunctionTester(unittest.TestCase):
triangularize_in_mel_space=True,
)
# fmt: off
# here the expected values from torchaudio.compliance.kaldi.get_mel_banks
# note that we compute values in float64 while they do it in float32
expected = np.array(
[[0.0000, 0.0000, 0.0000, 0.0000],
[0.6086, 0.0000, 0.0000, 0.0000],
[0.8689, 0.1311, 0.0000, 0.0000],
[0.4110, 0.5890, 0.0000, 0.0000],
[0.0036, 0.9964, 0.0000, 0.0000],
[0.0000, 0.6366, 0.3634, 0.0000],
[0.0000, 0.3027, 0.6973, 0.0000],
[0.0000, 0.0000, 0.9964, 0.0036],
[0.0000, 0.0000, 0.7135, 0.2865],
[0.0000, 0.0000, 0.4507, 0.5493],
[0.0000, 0.0000, 0.2053, 0.7947],
[0.0000, 0.0000, 0.0000, 0.9752],
[0.0000, 0.0000, 0.0000, 0.7585],
[0.0000, 0.0000, 0.0000, 0.5539],
[0.0000, 0.0000, 0.0000, 0.3599],
[0.0000, 0.0000, 0.0000, 0.1756]]
[
[0.0000000000000000, 0.0000000000000000, 0.0000000000000000, 0.0000000000000000],
[0.6457883715629578, 0.0000000000000000, 0.0000000000000000, 0.0000000000000000],
[0.8044781088829041, 0.1955219060182571, 0.0000000000000000, 0.0000000000000000],
[0.3258901536464691, 0.6741098165512085, 0.0000000000000000, 0.0000000000000000],
[0.0000000000000000, 0.9021250009536743, 0.0978749766945839, 0.0000000000000000],
[0.0000000000000000, 0.5219038724899292, 0.4780961275100708, 0.0000000000000000],
[0.0000000000000000, 0.1771058291196823, 0.8228941559791565, 0.0000000000000000],
[0.0000000000000000, 0.0000000000000000, 0.8616894483566284, 0.1383105516433716],
[0.0000000000000000, 0.0000000000000000, 0.5710380673408508, 0.4289619624614716],
[0.0000000000000000, 0.0000000000000000, 0.3015440106391907, 0.6984559893608093],
[0.0000000000000000, 0.0000000000000000, 0.0503356307744980, 0.9496643543243408],
[0.0000000000000000, 0.0000000000000000, 0.0000000000000000, 0.8150880336761475],
[0.0000000000000000, 0.0000000000000000, 0.0000000000000000, 0.5938932299613953],
[0.0000000000000000, 0.0000000000000000, 0.0000000000000000, 0.3851676583290100],
[0.0000000000000000, 0.0000000000000000, 0.0000000000000000, 0.1875794380903244],
],
dtype=np.float64,
)
# fmt: on
self.assertTrue(np.allclose(mel_filters, expected, atol=5e-5))
# kaldi implementation does not compute values for last fft bin
# indeed, they enforce max_frequency <= sampling_rate / 2 and
# therefore they know that last fft bin filter bank values will be all 0
# and pad after with zeros
# to comply with our API for `mel_filter_bank`, we need to also pad here
expected = np.pad(expected, ((0, 1), (0, 0)))
self.assertTrue(np.allclose(mel_filters, expected))
def test_mel_filter_bank_slaney_norm(self):
mel_filters = mel_filter_bank(
@@ -369,7 +381,7 @@ class AudioUtilsFunctionTester(unittest.TestCase):
self.assertTrue(np.allclose(spec[:64, 400], expected))
mel_filters = mel_filter_bank(
num_frequency_bins=256,
num_frequency_bins=257,
num_mel_filters=400,
min_frequency=20,
max_frequency=8000,
@@ -379,8 +391,6 @@ class AudioUtilsFunctionTester(unittest.TestCase):
triangularize_in_mel_space=True,
)
mel_filters = np.pad(mel_filters, ((0, 1), (0, 0)))
spec = spectrogram(
waveform,
window_function(400, "povey", periodic=False),
@@ -510,7 +520,7 @@ class AudioUtilsFunctionTester(unittest.TestCase):
self.assertTrue(np.allclose(spec_list[2][:64, 400], expected3))
mel_filters = mel_filter_bank(
num_frequency_bins=256,
num_frequency_bins=257,
num_mel_filters=400,
min_frequency=20,
max_frequency=8000,
@@ -520,8 +530,6 @@ class AudioUtilsFunctionTester(unittest.TestCase):
triangularize_in_mel_space=True,
)
mel_filters = np.pad(mel_filters, ((0, 1), (0, 0)))
spec_list = spectrogram_batch(
waveform_list,
window_function(400, "povey", periodic=False),